NURS 6512 Week 3 Diagnostic Tool Review Example

What a Result Changes: Appraising the Ottawa Ankle Rules and the Ages and Stages Questionnaire in Two Primary Care Scenarios

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College of Nursing, Walden University

NURS 6512: Advanced Health Assessment and Diagnostic Reasoning

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Month Day, Year

What a Result Changes: Appraising the Ottawa Ankle Rules and the Ages and Stages Questionnaire in Two Primary Care Scenarios

Introduction

A diagnostic tool is only as useful as the decision it informs. This review appraises two instruments that sit at opposite ends of primary care practice: the Ottawa ankle rules, a clinical decision rule used to decide whether an adult with an ankle injury needs radiography, and the Ages and Stages Questionnaire, Third Edition (ASQ-3), a parent-completed developmental screen. Each is examined under the same four headings, purpose and population, validity, reliability, and use in a composite scenario, so that the two can be compared on equal terms. Both scenarios are invented for this review.

The Ottawa Ankle Rules

Purpose and population

The Ottawa ankle rules were developed in Canadian emergency departments to reduce unnecessary ankle and foot radiographs in adults with acute blunt injury. An ankle series is indicated when there is pain in the malleolar zone together with bone tenderness along the distal 6 cm of the posterior edge or tip of either malleolus, or an inability to bear weight for four steps both immediately after the injury and at the time of examination. A parallel rule for the midfoot uses tenderness at the base of the fifth metatarsal or the navicular (Stiell et al., 1993). The rule was built and refined in adults, so any use in young children or in patients with altered sensation, intoxication, or multiple injuries falls outside the population in which it was tested.

Validity in usable terms

The rule was designed to miss almost no fractures, and it does. A systematic review of 27 studies found pooled sensitivity close to 98 percent and a negative likelihood ratio of about 0.08 for both the ankle and the midfoot (Bachmann et al., 2003). Specificity was far lower and varied widely between studies, which is the expected price of a rule tuned for sensitivity.

What this means at the bedside is that a negative result carries the weight and a positive one does not. If roughly 15 percent of adults presenting with an ankle injury have a fracture, the pretest odds are about 0.18. Multiplying by a negative likelihood ratio of 0.08 gives post-test odds near 0.014, or a fracture probability of about 1.4 percent, low enough that most clinicians would forgo imaging. A positive result, by contrast, raises the probability only modestly because many patients without fractures also meet the criteria. The rule therefore tells the clinician when an x-ray can safely be skipped, not when a fracture is present.

Reliability

Reliability asks whether two clinicians examining the same ankle would reach the same result. In the refinement and validation study, Stiell et al. (1993) reported good agreement between physicians applying the rule independently, which reflects its reliance on a small number of discrete, palpable landmarks rather than on overall impression. The weaker element is the weight-bearing criterion, since patients vary in how hard they try and examiners vary in what they count as a step.

The rule in a scenario

A 31-year-old man rolled his right ankle landing from a rebound in a recreational basketball game two hours ago. He limped into the clinic unassisted. There is swelling and tenderness anterior and inferior to the lateral malleolus over the anterior talofibular ligament, but palpation of the posterior edge and tip of both malleoli, the base of the fifth metatarsal, and the navicular is not tender. He takes four steps in the room. The rule is negative, the probability of fracture drops to roughly the level calculated above, and the next reasoning step shifts from whether a bone is broken to how severe the ligament sprain is and how it should be managed.

The Ages and Stages Questionnaire, Third Edition

Purpose and population

The ASQ-3 is a parent-completed developmental screen covering children from about 1 month to 5 1/2 years through age-specific questionnaires (Squires & Bricker, 2009). Each questionnaire asks six items in each of five domains, communication, gross motor, fine motor, problem solving, and personal-social, answered yes, sometimes, or not yet. Domain scores are compared with cutoffs set about two standard deviations below the normative mean, and scores between one and two standard deviations below fall in a monitoring zone. The tool screens; it does not diagnose, and it relies on the accuracy of a parent's observation. The American Academy of Pediatrics recommends standardized developmental screening at the 9-, 18-, and 30-month visits (Lipkin et al., 2020), and the ASQ-3 is one of the tools commonly used to meet that recommendation.

Validity in usable terms

The developers report overall sensitivity of about 86 percent and specificity of about 85 percent against standardized assessment in their normative sample (Squires & Bricker, 2009). Those figures sound close to the ankle rule, but they behave differently because developmental delay is less common in a general well-child population. If 15 of every 100 toddlers screened have a true delay, about 13 will screen positive correctly and 2 will be missed, while about 13 of the 85 without delay will also screen positive. Half of the positive screens are therefore false alarms, a positive predictive value near 50 percent. That is acceptable for a screen whose purpose is to prompt a fuller evaluation, and it is also why a positive ASQ-3 should never be presented to a family as a diagnosis.

Reliability

Because a parent completes the questionnaire, reliability depends on the parent. The developers report high test-retest agreement over two weeks and high agreement between parent and trained examiner scores (Squires & Bricker, 2009). In practice, reliability falls when a parent completes the form in the waiting room without being able to try items with the child, when literacy or language limits comprehension, or when a parent's worry or optimism colors the answers.

The tool in a scenario

A 24-month-old girl comes for a well-child visit. Her mother completes the 24-month ASQ-3, and the communication domain scores below the cutoff: the child uses about ten words and does not combine two words. The other four domains are above the monitoring zone. The result does not establish a language disorder, but it moves the next step from routine surveillance to action: a formal hearing evaluation, referral to early intervention for a developmental evaluation, and administration of the M-CHAT-R/F autism screen, which is recommended at this age and has its own follow-up interview to reduce false positives (Robins et al., 2014).

Limits Compared

The two tools fail in different places. The Ottawa rules are least trustworthy outside their validated population: in intoxicated patients, those with distracting injuries or neuropathy, and young children who cannot localize tenderness or cooperate with a four-step test. Within that population they are robust because they rest on discrete physical findings. The ASQ-3 is least trustworthy where the informant is least reliable and where prevalence is low, since its positive results will then be mostly false. It also depends on a parent's time, literacy, and language, which can reduce its accuracy for exactly the families who most need developmental support.

The shared lesson is that validity is not a property of a tool alone. It belongs to a tool used in a particular population for a particular decision, and a clinician who knows where each instrument was tested can tell when a result deserves to change the plan.

References

Bachmann, L. M., Kolb, E., Koller, M. T., Steurer, J., & ter Riet, G. (2003). Accuracy of Ottawa ankle rules to exclude fractures of the ankle and mid-foot: Systematic review. BMJ, 326(7386), 417. https://doi.org/10.1136/bmj.326.7386.417

Lipkin, P. H., Macias, M. M., & Council on Children With Disabilities, Section on Developmental and Behavioral Pediatrics. (2020). Promoting optimal development: Identifying infants and young children with developmental disorders through developmental surveillance and screening. Pediatrics, 145(1), e20193449. https://doi.org/10.1542/peds.2019-3449

Robins, D. L., Casagrande, K., Barton, M., Chen, C. M. A., Dumont-Mathieu, T., & Fein, D. (2014). Validation of the Modified Checklist for Autism in Toddlers, Revised With Follow-up (M-CHAT-R/F). Pediatrics, 133(1), 37-45. https://doi.org/10.1542/peds.2013-1813

Squires, J., & Bricker, D. (2009). Ages & Stages Questionnaires, third edition (ASQ-3): A parent-completed child monitoring system. Paul H. Brookes.

Stiell, I. G., Greenberg, G. H., McKnight, R. D., Nair, R. C., McDowell, I., Reardon, M., Stewart, J. P., & Maloney, J. (1993). Decision rules for the use of radiography in acute ankle injuries: Refinement and prospective validation. JAMA, 269(9), 1127-1132. https://doi.org/10.1001/jama.1993.03500090063034